Abstract CS1-1: Oligometastatic disease: Definitions and practice patterns

Abstract

Abstract Available evidence on oligometastatic disease (OMD) and its treatment, more in particular the use of metastasis directed radiotherapy (MDRT), mostly derives from retrospective, single-center series, with significant heterogeneity in patient inclusion criteria, definition of OMD, and outcomes reported. No molecular biomarker being clinically available for the identification of patients with true OMD, its diagnosis is typically based on imaging findings. However, the presentation on imaging may represent a whole range of different clinical scenarios, depending on the moment in the disease history, and the use - or not - of systemic therapy. Based on the available data, consensus was reached amongst radiation oncology experts representing ASTRO and ESTRO, that OMD can to date be defined as 1-5 metastatic lesions, both occurring synchronously or metachronously, in which a controlled primary tumor is considered optional but with as prerequisite that all metastatic sites must be safely treatable. Moreover, in a collaboration between the ESTRO and EORTC, subclassification into oligorecurrence, oligoprogression, and oligopersistence was suggested, depending on whether OMD is diagnosed during a treatment-free interval or during active systemic therapy and whether or not an oligometastatic lesion is progressing on current imaging.While further evidence is being generated in (randomized) clinical trials as well as through collecting real-world data from clinical practice, it is imperative to use consistent definitions and reporting to further refine and validate the OMD classification and nomenclature, and to acquire a better understanding of the true impact of MDRT in different clinical scenarios. Citation Format: Y Lievens. Oligometastatic disease: Definitions and practice patterns [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr CS1-1.